Juwon Jeong

Reactively sputtered nickel nitride as electrocatalytic counter electrode for dye- and quantum dot-sensitized solar cells

Nickel nitride electrodes were prepared by reactive sputtering of nickel under a N2 atmosphere at room temperature for application in mesoscopic dye- or quantum dot- sensitized solar cells. This facile and reliable method led to the formation of a Ni2N film with a cauliflower-like nanostructure and tetrahedral crystal lattice. The prepared nickel nitride electrodes exhibited an excellent chemical stability toward both iodide and polysulfide redox electrolytes. Compared to conventional Pt electrodes, the nickel nitride electrodes showed an inferior electrocatalytic activity for the iodide redox electrolyte; however, it displayed a considerably superior electrocatalytic activity for the polysulfide redox electrolyte. As a result, compared to dye-sensitized solar cells (DSCs), with a conversion efficiency (η) = 7.62%, and CdSe-based quantum dot-sensitized solar cells (QDSCs, η = 2.01%) employing Pt counter electrodes (CEs), the nickel nitride CEs exhibited a lower conversion efficiency (η = 3.75%) when applied to DSCs, but an enhanced conversion efficiency (η = 2.80%) when applied to CdSe-based QDSCs.

Comparison of the Pathogenesis of Single or Dual Infections with Type 1 and Type 2 Porcine Reproductive and Respiratory Syndrome Virus

The aim of this study was to compare the pathogenicity of single or dual infections with type 1 and type 2 porcine reproductive and respiratory syndrome virus (PRRSV) in pigs. Pigs were inoculated intranasally with type 1 or type 2 PRRSV or both viruses together. Pigs infected with type 1 and type 2 PRRSV together had significantly (P <0.05) fewer genomic copies of type 1 PRRSV than did pigs infected with type 1 PRRSV alone. Pigs infected with type 2 PRRSV alone or type 1 and type 2 PRRSV together had significantly (P <0.05) higher gross and microscopical lung lesion scores than did pigs infected with type 1 PRRSV alone. Pigs infected with type 2 PRRSV alone or type 1 and type 2 PRRSV together had significantly (P <0.05) higher scores for PRRSV-positive cells in the lung than did pigs infected with type 1 PRRSV alone. Pigs infected with type 1 PRRSV alone had significantly (P <0.05) higher scores for type 1 PRRSV-positive cells in the lung than did pigs infected with both types of PRRSV together. Pigs infected with both types of PRRSV together developed similar clinical disease and lesions as pigs infected with type 2 PRRSV alone. Significant differences in virulence were not observed between pigs infected with type 2 PRRSV alone and pigs infected with both types of PRRSV together in terms of viraemia, lung lesion score and virus distribution within lung lesions.

Comparison of commercial type 1 and type 2 PRRSV vaccines against heterologous dual challenge

This study was to compare the effect of vaccination of pigs with either type 1 or type 2 porcine reproductive and respiratory syndrome virus (PRRSV) against heterologous dual challenge of both genotypes. Pigs were administered type 1 (UNISTRAIN PRRS) or type 2 (Fostera PRRS) PRRSV vaccine at 28 days of age and inoculated intranasally with both genotypes at 63 days of age. Vaccination of pigs with type 1 PRRSV was able to reduce the levels of type 1 but not type 2 PRRSV viraemia, whereas vaccination of pigs with type 2 PRRSV was able to reduce the levels of type 1 and type 2 PRRSV viraemia against a dual challenge. Vaccination of pigs with type 2 PRRSV significantly reduced lung lesions after dual challenge compared with vaccination of pigs with type 1 PRRSV. Vaccination of pigs with type 2 PRRSV induced higher numbers of type 1 and type 2 PRRSV-specific interferon-γ secreting cells compared with vaccination of pigs with type 1 PRRSV after dual challenge. The results of this study demonstrated that vaccination of pigs with type 2 PRRSV is efficacious in protecting growing pigs from respiratory disease after heterologous dual type 1 and type 2 PRRSV challenge compared with vaccination of pigs with type 1 PRRSV.

Wrinkled silica/titania nanoparticles with tunable interwrinkle distances for efficient utilization of photons in dye-sensitized solar cells.

Efficient light harvesting is essential for the realization of high energy conversion efficiency in dye-sensitized solar cells (DSCs). State-of-the-art mesoporous TiO2 photoanodes fall short for collection of long-wavelength visible light photons, and thus there have been efforts on introduction of scattering nanoparticles. Herein, we report the synthesis of wrinkled silica/titania nanoparticles with tunable interwrinkle distances as scattering materials for enhanced light harvesting in DSCs. These particles with more than 20 times larger specific surface area (>400 m2/g) compared to the spherical scattering particles (<20 m2/g) of the similar sizes gave rise to the dye-loading amounts, causing significant improvements in photocurrent density and efficiency. Moreover, dependence of spectral scattering properties of wrinkled particles on interwrinkle distances, which was originated from difference in overall refractive indices, was observed.

Solvothermal-Derived S-Doped Graphene as an Anode Material for Sodium-Ion Batteries

Abstract Sodium‐ion batteries (SIBs) have attracted enormous attention in recent years due to the high abundance and low cost of sodium. However, in contrast to lithium‐ion batteries, conventional graphite is unsuitable for SIB anodes because it is much more difficult to intercolate the larger Na ions into graphite layers. Therefore, it is critical to develop new anode materials for SIBs for practical use. Here, heteroatom‐doped graphene with high doping levels and disordered structures is prepared using a simple and economical thermal process. The solvothermal‐derived graphene shows excellent performance as an anode material for SIBs. It exhibits a high reversible capacity of 380 mAh g−1 after 300 cycles at 100 mA g−1, excellent rate performance 217 mAh g−1 at 3200 mA g−1, and superior cycling performance at 2.0 A g−1 during 1000 cycles with negligible capacity fade.

Electrochemically Synthesized Nanoporous Molybdenum Carbide as a Durable Electrocatalyst for Hydrogen Evolution Reaction

Abstract Demands for sustainable production of hydrogen are rapidly increasing because of environmental considerations for fossil fuel consumption and development of fuel cell technologies. Thus, the development of high‐performance and economical catalysts has been extensively investigated. In this study, a nanoporous Mo carbide electrode is prepared using a top‐down electrochemical process and it is applied as an electrocatalyst for the hydrogen evolution reaction (HER). Anodic oxidation of Mo foil followed by heat treatment in a carbon monoxide (CO) atmosphere forms a nanostructured Mo carbide with excellent interconnections, and these structural characteristics lead to high activity and durability when applied to the HER. Additionally, characteristic behavior of Mo is observed; metallic Mo nanosheets form during electrochemical anodization by exfoliation along the (110) planes. These nanosheets are viable for chemical modification, indicating their feasibility in various applications. Moreover, the role of carbon shells is investigated on the surface of the electrocatalysts, whereby it is suggested that carbon shells serve as a mechanical barrier against the oxidative degradation of catalysts that accompanies unavoidable volume expansion.

In-situ Hybridization for the Detection of Sacbrood Virus in Infected Larvae of the Honey Bee (Apis cerana)

The aim of this study was to develop and use in-situ hybridization (ISH) for the detection and localization of the sacbrood virus (SBV) in Korean honey bee (Apis cerana) larvae that were infected naturally with SBV. A 258 base pair cDNA probe for SBV was generated by polymerase chain reaction. Cells positive for viral genome typically showed a dark brown reaction in the cytoplasm. SBV was detected consistently in trophocytes and urocytes. The ISH was successfully applied to routinely fixed and processed tissues and thus should prove helpful in the diagnosis and characterization of viral distribution in infected larvae.

Two Commercial Type 1 Porcine Reproductive and Respiratory Syndrome Virus (PRRSV)-Modified Live Vaccines Reduce Seminal Shedding of Type 1 PRRSV but not Type 2 PRRSV in Infected Boars

&NA; The objective of this study was to compare the effects of two commercial type 1 porcine reproductive and respiratory syndrome virus (PRRSV)‐modified live vaccines on type 1 and type 2 PRRSV shedding in the semen of experimentally infected boars. Upon challenge with PRRSV, unvaccinated boars exhibited an increase in daily rectal temperature (39.4–39.7°C). Vaccination of boars with type 1 PRRSV significantly reduced the amount of type 1 PRRSV load in blood and semen after challenge with type 1 PRRSV, but barely reduced the amount of type 2 PRRSV load in blood and semen after the type 2 PRRSV challenge. There were no significant differences in the reduction of viremia and seminal shedding of type 1 and type 2 PRRSV between the two commercial vaccines. The seminal shedding of PRRSV is independent of viremia. The reduction of type 1 PRRSV seminal shedding coincided with the appearance of type 1 PRRSV‐specific interferon‐γ secreting cells (IFN‐γ‐SC) in vaccinated type 1 PRRSV‐challenged boars. The frequencies of type 1 PRRSV‐specific IFN‐γ‐SC induced by type 1 PRRSV vaccine are relatively high compared to type 2 PRRSV‐specific IFN‐γ‐SC induced by the same vaccine which may explain why type 1 PRRSV vaccine is more effective in reducing seminal shedding of type 1 PRRSV when compared to type 2 PRRSV in vaccinated challenged boars. These results provide clinical information on how to reduce seminal shedding of type 1 PRRSV in boars using type 1 PRRSV‐modified live vaccine.

Highly Efficient Bifacial Dye-Sensitized Solar Cells Employing Polymeric Counter Electrodes

Dye-sensitized solar cells (DSCs) are promising solar energy conversion devices with aesthetically favorable properties such as being colorful and having transparent features. They are also well-known for high and reliable performance even under ambient lighting, and these advantages distinguish DSCs for applications in window-type building-integrated photovoltaics (BIPVs) that utilize photons from both lamplight and sunlight. Therefore, investigations on bifacial DSCs have been done intensively, but further enhancement in performance under back-illumination is essential for practical window-BIPV applications. In this research, highly efficient bifacial DSCs were prepared by a combination of electropolymerized poly(3,4-ethylenedioxythiphene) (PEDOT) counter electrodes (CEs) and cobalt bipyridine redox ([Co(bpy)3]3+/2+) electrolyte, both of which manifested superior transparency when compared with conventional Pt and iodide counterparts, respectively. Keen electrochemical analyses of PEDOT films verified that superior electrical properties were achievable when the thickness of the film was reduced, while their high electrocatalytic activities were unchanged. The combination of the PEDOT thin film and [Co(bpy)3]3+/2+ electrolyte led to an unprecedented power conversion efficiency among bifacial DSCs under back-illumination, which was also over 85% of that obtained under front-illumination. Furthermore, the advantage of the electropolymerization process, which does not require an elevation of temperature, was demonstrated by flexible bifacial DSC applications.

Tailoring the porosity of MOF-derived N-doped carbon electrocatalysts for highly efficient solar energy conversion

Metal–organic framework (MOF)-derived carbon materials have been widely used as catalysts for a variety of electrochemical energy applications, and thermally carbonized zinc-2-methylimidazole (ZIF-8) has shown particularly high performance owing to its microporous structure with a large surface area. However, in the presence of bulky chemical species, such as triiodide, in mesoscopic dye-sensitized solar cells (DSCs), the small pore size of carbonized ZIF-8 causes a significant limitation in mass transfer and consequentially results in a poor performance. To resolve this problem, we herein report a simple strategy to enlarge the pore sizes of ZIF-8-derived carbon by increasing the dwelling time of Zn in ZIF-8 during the thermal carbonization process. A thin and uniform polydopamine shell introduced on the surface of ZIF-8, with the aim of retarding the escape of vaporized Zn species, leads to a dramatic increase in pore sizes, from the micropore to mesopore range. The porosity-tailored carbonized ZIF-8 manifests an excellent electrocatalytic performance in triiodide reduction, and when it was applied as the counter electrode of DSCs, an energy conversion efficiency of up to 9.03% is achievable, which is not only superior to that of the Pt-based counterpart but also among the highest performances of DSCs employing carbonaceous electrocatalysts.